KVM: arm/arm64: Move timer save/restore out of the hyp code

As we are about to be lazy with saving and restoring the timer
registers, we prepare by moving all possible timer configuration logic
out of the hyp code.  All virtual timer registers can be programmed from
EL1 and since the arch timer is always a level triggered interrupt we
can safely do this with interrupts disabled in the host kernel on the
way to the guest without taking vtimer interrupts in the host kernel
(yet).

The downside is that the cntvoff register can only be programmed from
hyp mode, so we jump into hyp mode and back to program it.  This is also
safe, because the host kernel doesn't use the virtual timer in the KVM
code.  It may add a little performance performance penalty, but only
until following commits where we move this operation to vcpu load/put.

Signed-off-by: Christoffer Dall <cdall@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

6 files changed, 15 insertions, 10 deletions

diff --git a/arch/arm/include/asm/kvm_asm.h b/arch/arm/include/asm/kvm_asm.h
index 14d68a4d826f..36dd2962a42d 100644
--- a/arch/arm/include/asm/kvm_asm.h
+++ b/arch/arm/include/asm/kvm_asm.h
@@ -68,6 +68,8 @@ extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
 extern void __kvm_tlb_flush_vmid(struct kvm *kvm);
 extern void __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu);
 
+extern void __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high);
+
 extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
 
 extern void __init_stage2_translation(void);
diff --git a/arch/arm/include/asm/kvm_hyp.h b/arch/arm/include/asm/kvm_hyp.h
index 14b5903f0224..ab20ffa8b9e7 100644
--- a/arch/arm/include/asm/kvm_hyp.h
+++ b/arch/arm/include/asm/kvm_hyp.h
@@ -98,8 +98,8 @@
 #define cntvoff_el2			CNTVOFF
 #define cnthctl_el2			CNTHCTL
 
-void __timer_save_state(struct kvm_vcpu *vcpu);
-void __timer_restore_state(struct kvm_vcpu *vcpu);
+void __timer_enable_traps(struct kvm_vcpu *vcpu);
+void __timer_disable_traps(struct kvm_vcpu *vcpu);
 
 void __vgic_v2_save_state(struct kvm_vcpu *vcpu);
 void __vgic_v2_restore_state(struct kvm_vcpu *vcpu);
diff --git a/arch/arm/kvm/hyp/switch.c b/arch/arm/kvm/hyp/switch.c
index ebd2dd46adf7..330c9ce34ba5 100644
--- a/arch/arm/kvm/hyp/switch.c
+++ b/arch/arm/kvm/hyp/switch.c
@@ -174,7 +174,7 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 	__activate_vm(vcpu);
 
 	__vgic_restore_state(vcpu);
-	__timer_restore_state(vcpu);
+	__timer_enable_traps(vcpu);
 
 	__sysreg_restore_state(guest_ctxt);
 	__banked_restore_state(guest_ctxt);
@@ -191,7 +191,8 @@ again:
 
 	__banked_save_state(guest_ctxt);
 	__sysreg_save_state(guest_ctxt);
-	__timer_save_state(vcpu);
+	__timer_disable_traps(vcpu);
+
 	__vgic_save_state(vcpu);
 
 	__deactivate_traps(vcpu);
@@ -237,7 +238,7 @@ void __hyp_text __noreturn __hyp_panic(int cause)
 
 		vcpu = (struct kvm_vcpu *)read_sysreg(HTPIDR);
 		host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
-		__timer_save_state(vcpu);
+		__timer_disable_traps(vcpu);
 		__deactivate_traps(vcpu);
 		__deactivate_vm(vcpu);
 		__banked_restore_state(host_ctxt);
diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 26a64d0f9ab9..ab4d0a926043 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -55,6 +55,8 @@ extern void __kvm_tlb_flush_vmid_ipa(struct kvm *kvm, phys_addr_t ipa);
 extern void __kvm_tlb_flush_vmid(struct kvm *kvm);
 extern void __kvm_tlb_flush_local_vmid(struct kvm_vcpu *vcpu);
 
+extern void __kvm_timer_set_cntvoff(u32 cntvoff_low, u32 cntvoff_high);
+
 extern int __kvm_vcpu_run(struct kvm_vcpu *vcpu);
 
 extern u64 __vgic_v3_get_ich_vtr_el2(void);
diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
index 4572a9b560fa..08d3bb66c8b7 100644
--- a/arch/arm64/include/asm/kvm_hyp.h
+++ b/arch/arm64/include/asm/kvm_hyp.h
@@ -129,8 +129,8 @@ void __vgic_v3_save_state(struct kvm_vcpu *vcpu);
 void __vgic_v3_restore_state(struct kvm_vcpu *vcpu);
 int __vgic_v3_perform_cpuif_access(struct kvm_vcpu *vcpu);
 
-void __timer_save_state(struct kvm_vcpu *vcpu);
-void __timer_restore_state(struct kvm_vcpu *vcpu);
+void __timer_enable_traps(struct kvm_vcpu *vcpu);
+void __timer_disable_traps(struct kvm_vcpu *vcpu);
 
 void __sysreg_save_host_state(struct kvm_cpu_context *ctxt);
 void __sysreg_restore_host_state(struct kvm_cpu_context *ctxt);
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 945e79c641c4..4994f4bdaca5 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -298,7 +298,7 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
 	__activate_vm(vcpu);
 
 	__vgic_restore_state(vcpu);
-	__timer_restore_state(vcpu);
+	__timer_enable_traps(vcpu);
 
 	/*
 	 * We must restore the 32-bit state before the sysregs, thanks
@@ -368,7 +368,7 @@ again:
 
 	__sysreg_save_guest_state(guest_ctxt);
 	__sysreg32_save_state(vcpu);
-	__timer_save_state(vcpu);
+	__timer_disable_traps(vcpu);
 	__vgic_save_state(vcpu);
 
 	__deactivate_traps(vcpu);
@@ -436,7 +436,7 @@ void __hyp_text __noreturn __hyp_panic(void)
 
 		vcpu = (struct kvm_vcpu *)read_sysreg(tpidr_el2);
 		host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
-		__timer_save_state(vcpu);
+		__timer_disable_traps(vcpu);
 		__deactivate_traps(vcpu);
 		__deactivate_vm(vcpu);
 		__sysreg_restore_host_state(host_ctxt);